Contour Enthusiasts Group Archives Forums General Dyno and Drag Inflated crank horsepower ratings

In reviewing Suneil's impressive 401 wheel horsepower rating, a local pope said the following about crank horsepower:

Quote:

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For the reverse bench racing folks that's edging near the 500 CRANK HP mark.

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Is there any real reason that 400 wheel horsepower would relate to 500-ish crank horsepower?

Think about this logically: crank power is obviously greater than wheel power because of drivetrain losses through the trans, diff, etc. Look at a stock 2.5 SVT dyno (usually shows about 165-ish hp, compared to 200-ish crank hp) - that indicates to me that losses are about 35-ish hp.

Is there any reason to believe a high-boost 2.5 turbo has 100-ish hp of losses, compared to 35-ish for stock? Obviously not. This defies logic. Losses cannot increase just because output has increased. It still takes the same torque to overcome friction in the trans, etc. A neat turbo sitting upstream doesn't suddenly make the drivetrain 3 times harder to turn.

I understand that the 1.20-1.25 factor for crank to wheel power can be a useful tool, but to use it to calculate 500 crank hp is ridiculous.

Regardless, I am very impressed with Suneil's 401 whp/436 chp motor.

You increase power, you increase the quantative that will be lost through the tranny. It's by a percentage, and yeah it's probably not quite 500 crank HP, but it's atleast 485hp at the crank.

I always assume an 18% loss, so divide 401 by .82 = 489 crank hp.

If we assume 18% loss...I multiply the 401 by 118% or 1.18 to get 473.18 crank hp. The only real way to find out I suppose would be to throw it on an engine dyno, but I don't really think Sun cares that much...

Jim who's math is correct?

i'm just happy it runs. . .
not that I had doubts. . .but crank vs. at the wheel, in my book, it's what you put down that counts, because it has to go through the driveline loss to make it there, so i won't be happy until I hit 500 at the wheels, which I'll never attempt to do, because I just don't see it happening without nitrous or some SERIOUS tricks (ice in the intercooler, nice cool day, iced UIM, etc.)

Who knows, Demon says the block can take 1200hp
The crank, should at least be able to take 800hp (that's from memory).
The forged rods could take 800hp, the total ring seals are optimized for the FI setup, so shouldn't have to worry about the pistons melting. . .I dunno, no one has pushed 20psi on a 2.5L setup yet, so who's to say what could be had. . .ok, ramble off.

well then why dont you throw 20lbs. on that azz one time and see what happens?

what size injectors are you running?

119 ocatane